Yeah, but orphaning a single PoS block with 2 PoW blocks actually costs you something (you have to be lucky or have majority of the network's hashrate).
It seems that there's currently a pool in a position to make it happen on a frequent ongoing basis. Orphaning a PoS block with 2 PoW blocks doesn't really cost you anything
extra if you're already PoW mining anyway and happen to hit 2 consecutive PoW blocks.
Nope, the rogue PoW miner has to decide in advance to invest his work in what will most probably be an invalid chain. So when he fails to execute his attack, he effectively lost his potential profit from playing nice.
OTOH, with PoS you can safely and with absolutely no additional cost mine on all the forks.
In the current scenario where one pool actually does have majority hashpower, this isn't quite true. Of course, the bigger problem isn't that issue, it's that there's one pool with majority hashpower at all.. Perhaps this should be a larger item of concern for the YACoin community at the moment.
The gain in the miner's held YAC from orphaning PoS blocks is zero, but there may be other motivations other than an immediate gain in YAC to orphan PoS blocks.
I fail to see any possible motivation to do so whatsoever.
The cryptocurrency community contains a certain number of people who like to be a dick, and will do things solely for the purpose of being as much of a dick as possible. I think Luke-Jr possibly sets a good example of how best to be a dick to many altcoins.